1. Field of the Invention
The present invention relates to connection control equipment. More particularly, it relates to connection control equipment for use in a communication system for simultaneously providing services for a number of terminals, which is capable of identifying each terminal requesting multi-channel communication services by a calling number and a calling sub-address, or by user-to-user information in a message, and which correlates calls of a calling user terminal.
2. Description of the Prior Art
Japanese Laid-open Patent Publication No. 5-48721 (reference (1)) discloses conventional connection control equipment for switching circuits in an exchange. It receives a telephone call over an integrated service digital network (ISDN); and determines a receiving terminal number by an ISDN user-to-user information, as a retrieval key other than the calling number, and may connect it to a selected receiving terminal number in view of, e.g., sex and (or) department of the calling person, to correctly respond to the requirement of the calling person.
Japanese Laid-open Patent Publication No. 3-3449 (reference (2)) discloses connection control equipment that can select a suitable one of prepared modems by an electronic switch at its receiving side. This means that the need for determining a type of modem is eliminated and time and operation of checking the modem for its adaptability are saved.
Japanese Laid-open Patent Publication No. 3-26194 (reference (3)) discloses connection control equipment which is capable of identifying a group of the automatic call distribution (ACD) by the calling number in an ISDN protocol and distributing incoming calls among receiving terminals within the ACD group depending upon traffic charge to the group. Thereby, distributed connections for each area of the calling parties are realized.
Japanese Laid-open Patent Publication No. 3-85858 (reference (4)) discloses connection control equipment which includes the ability to identify a calling number in a call-setting message of a call transmitted over an ISDN for connecting a private exchange to the ISDN and the ability to determine a kind of service to be provided for the incoming call according to the call-setup message. It can provide different calling subscribers with different services for the calls incoming over an ISDN.
In a communication system that provides services over two B-channels of an ISDN (Integrated Service Digital Network), a calling terminal and an information processing adapter (a called terminal) are connected through respective basic interfaces to the public network of the ISDN. The information processing adapter compresses service data received from the host computer and transmits them to the calling terminal over the ISDN by using two B-channels of the ISDN line. It also receives and expands service data transmitted from the terminal through two B-channels of the ISDN line and transfers them to the host computer.
The following is a connection control procedure for communications by using two B-channels.
In this case, terminal (caller) makes a call request (first call over one of the two B-channel) by dialing a telephone number allocated to a line connected to the information processing adapter (called terminal). After connection of the call to the information processing adapter communication conditions are negotiated between the calling and called terminals. If the negotiation is concluded to provide two B-channel services, the terminal makes a call request (a second call over the other B-channel) by dialing a telephone number allocated to the line connected to the information processing adapter (called terminal). The two B-channels from the calling terminal are thus connected to the called terminal through which the required service can be provided.
Furthermore, in a communication system which is capable of communicating with a plurality of outside terminals at a time by using conventional switching equipment accommodating a plurality information processing adapters (private-side terminals), the information processing adapters are each connected by a bus line to the host computer. The bus topology enables all the information processing adapters to receive and transmit service data to and from the computer at a time.
The following is a connection control procedure for communication by using two B-channels.
The calling terminals make each a first call request (over the first B-channel) by dialing a representative telephone number allocated to a group of lines connected to the switching system and respective private line numbers of the information processing adapters (called terminals). The switching system selects the respective information processing adapters by the private line numbers and connects the calls from the terminals to the corresponding information processing adapters.
After connection of the calls to the information processing adapters both parties negotiate with each other as to communication conditions over the connected lines. If the negotiations are concluded to provide two B-channel services, the terminals make each a second call request (over the second B-channel) by dialing a representative telephone number allocated to a group of lines connected to the exchange unit and respective private line numbers of the information processing adapters (called terminals). The two B-channels from the calling terminals are thus connected to the information processing adapters through which the required services can be provided.
As described above, the communication system using conventional switching equipment requires a user of a calling terminal to specify a private line number of an information processing adapter (called terminal) when requesting connection of two calls to the designated adapter.
However, it is desirable that a calling party makes two calls without dialing a private line number of an information processing adapter. It is further desirable to have a switching system automatically control connection of the two calls to the same adapter if services, to be requested by the caller and to be supplied from the computer through each information processing adapter, are the same.